From 30e69bccee56b3e7a106df91b28b050884b3ad3c Mon Sep 17 00:00:00 2001
From: yuvipanda <yuvipanda@gmail.com>
Date: Mon, 10 Dec 2018 23:06:07 -0800
Subject: [PATCH] Add unit test for execute_cmd in repo2docker.utils

---
 repo2docker/utils.py |  4 +++-
 tests/test_utils.py  | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 1 deletion(-)
 create mode 100644 tests/test_utils.py

diff --git a/repo2docker/utils.py b/repo2docker/utils.py
index d6854c8f..ce0f470b 100644
--- a/repo2docker/utils.py
+++ b/repo2docker/utils.py
@@ -10,7 +10,9 @@ from traitlets import Integer, TraitError
 
 def execute_cmd(cmd, capture=False, **kwargs):
     """
-    Call given command, yielding output line by line if capture=True
+    Call given command, yielding output line by line if capture=True.
+
+    Must be yielded from.
     """
     if capture:
         kwargs['stdout'] = subprocess.PIPE
diff --git a/tests/test_utils.py b/tests/test_utils.py
new file mode 100644
index 00000000..17c78aa0
--- /dev/null
+++ b/tests/test_utils.py
@@ -0,0 +1,37 @@
+"""
+Tests for repo2docker/utils.py
+"""
+from repo2docker import utils
+import pytest
+import subprocess
+
+
+def test_capture_cmd_no_capture_success():
+    # This should succeed
+    for line in utils.execute_cmd([
+        '/bin/bash', '-c', 'echo test'
+    ]):
+        pass
+
+def test_capture_cmd_no_capture_fail():
+    with pytest.raises(subprocess.CalledProcessError):
+        for line in utils.execute_cmd([
+            '/bin/bash', '-c', 'e '
+        ]):
+            pass
+
+
+def test_capture_cmd_capture_success():
+    # This should succeed
+    for line in utils.execute_cmd([
+        '/bin/bash', '-c', 'echo test'
+    ], capture=True):
+        assert line == 'test\n'
+
+
+def test_capture_cmd_capture_fail():
+    with pytest.raises(subprocess.CalledProcessError):
+        for line in utils.execute_cmd([
+            '/bin/bash', '-c', 'echo test; exit 1 '
+        ], capture=True):
+            assert line == 'test\n'
\ No newline at end of file